Weird screeching noise

Hi all - I was running my 1989 classic with twin 3208TA's the other day at 2400 RPM when all of the sudden I heard this fairly loud screeching noise...People in the salon thought the noise was coming from the rear stateroom area. I was on the bridge...I backed it down and put it neutral imediately. The noise went away and while I left the engines running in neutral, I went down to the engine room and everything seemed normal. I then put it in gear and slowly brought the RPM's back up to 2400. The noise never came back. Later while someone else was driving I went down to the engine room and checked temps with my infared thermometer...all engine and shaft seal temps were normal. I am wondering if it could of been a cutless bearing behind the shaft seals?? Has anybody experienced anything like this? Thanks

Not sure about dampner plates on 3208s, but same sound and reaction to rpms on my Lehman.

Could not reproduce symptom till a spring came apart and a piece siezed my flywheel and choked off the engine. Not serious, but needed to be replaced.

Cant say thats what you have but the noise was horrific. Thought the engine was coming apart and the smoke from friction set off smoke detector in engine room.

Are you positive of the area where the sound was heard?

Its gotta be a dry bearing somewhere. Trust me, it will repeat itself.

pete

I hate strange noises like that. I'm like ok, c'mon, hurry up and break already, don't leave me hanging.

Cutlass?

Greetings,
Mr l. Loose fan belt?

Hi Lanceolson,

RT Firefly said:

Greetings,
Mr l. Loose fan belt?

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RT Firefly's opinion matches my own. Particularly if you were early-on in a cruise with depleted batteries, and one or both of your alternators were in full-tilt charge mode. I can't explain why the noise didn't return after running back up to full throttle, but perhaps you either increased power more gradually, or I'm full of more s$%^ that a Christmas goose.

You might check the temp of your alternators while underway in similar circumstances. If they're running more than about 160 deg f, you may well have an alternator bearing starting to yell at you.

Regards,

Pete

On the AT, there is a grounding carbon brush riding on the shaft. It occasionally will squeal. Last time I was in the yard, I mentioned it and they lifted the assembly and bent so it rides harder against the shaft, presto, noise gone.
If it happens underway, I guess I could go back, lift it so it rides a bit differently.

jungpeter said:

RT Firefly's opinion matches my own. Particularly if you were early-on in a cruise with depleted batteries, and one or both of your alternators were in full-tilt charge mode. I can't explain why the noise didn't return after running back up to full throttle, but perhaps you either increased power more gradually, or I'm full of more s$%^ that a Christmas goose.

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Agreed. Load could have been reduced later due to battery recovery or temperature regulation.

I'd check belt condition and tension before anything else.

Mine was the shaft carbon brush as well.

I experienced a similar event, and from time to time over the next day or so it would return. Turned out that salt had accumulated in the nipple going into the port shaft log aft of the dripless shaft packing. I guess when the engine was shutdown, the heat of the ER dried out the water remaining just at the waterline of the boat. Things heated up and contact eventuated with the accompanying screech. Easy to check and correct.

I had a frightening banging noise when cruising, it lasted about a minute as I was shutting down, stopping the engine.
Couldn't see anything wrong, engine ran fine afterwards and we got safely to port .
Further checks revealed g/box oil in the engine room, dry g/box.
Stripped gearbox for o/haul and discovered it was completely shot internally and had badly scored the interior casing, wrecked the drive plate and severely cracked the bell housing.
Needing new g/box, drive plate, bell housing and oil cooler.
Investigation revealed that when the boat was built it was mounted on 4 engine mounts, 2 at the front of the engine, and 2 on the gearbox which over time and heavy use caused a 'sagging' stress on the bell housing gearbox gasket joints.
It should have been built with 2 engine mountings at the front and 2 at the rear of the engine on the bell housing.
Its also worth noting here that engine mountings have what's called a 'Shore rating' (resistance to vibration/weight carrying capacity) the PO had used standard front engine mounts all round when replacing them at some stage.
The rear engine mounts have to carry the flywheel and the heavy front end of the gearbox and must be stiffer stronger to carry the extra weight.
A very expensive repair which could have been avoided with an earlier modification if I had 20/20 hindsight, I've been around engines for many years and never come across this problem before.
Its further compounded by travel restrictions due to Covid and closed borders (we're in the South of France and the new g/box is in England).
I wonder if you'll check/modify your engine gearbox mountings and learn from my experience ?
Or, will you just say 'Its been fine up to now so why worry' ! It'll cost you someday if you do.......

The front bearing on an alternator can make screeching noises when it runs out of lube.
But I would check out the belt first.

I had a similar screeching sound come from my stuffing box area at higher RPMs; it went away at lower speeds so we limped back in to the marina. Turned out there was a dry cutless bearing right behind the shaft seal, due to lack of water getting to the bearing.

We bought our boat from a hire company called Le Boat (never buy a boat from them) it was all we could afford at that time.
We found that instead of their (maintenance engineers, for that read 'Redneck Ham Fisted Bodgits) greasing/repacking the stern gland they just kept overtightening it.
Consequently when we bought the boat and had her lifted out we withdrew the shaft to check for alignment and discovered the shaft had a groove worn in it from running dry and overtightening.
I was able to turn the shaft end over end and fitted a PSS seal.
Many thousands of miles later its still running perfectly.

I'm with those mentioning alt belt as I have had similar sometimes erratic occurrences when belt has stretched and becoming loose. Mine seemed to occur after starting and beginning to rev up.
A different rate of increase avoided the noise temporarily but tightening the belt solved the problem.

raw water pump going?

I would also check the raw water pump belts and bearings.

You can look for leaks and maybe compare the temperatures of the pumps in the two engines with an infrared themometer while underway.

This addresses the initial purchase of the boat and if it does not fit here, feel free to relocate my comments to the proper forum.

I am not intentionally comparing boat brokers and surveyors to the stereo typed "used car salesman" but, ....
If they were a bit more honest the industry would benefit.
Maybe they don't have the time nor desire to investigate the condition of each boat. They seem to be willing to accept the owners opinion.
Their reputation hangs on each sale. Alas, there is no 'clearing house' for brokers and surveyors. Their professional organizations seem to be operating as a 'shield' of its members. Yes, there are initial educational and testing requirements but, once a member, always a member. To my knowledge, there is no ongoing CEU requirements.
Like all professions, there are good and bad folks.
Alas, the brokers and surveyors hide behind their 'Disclaimer' statement. Maybe one day a new, naive boat owner will take the broker or surveyor before their professional organization and or the civil court.
I will end by saying, my broker was IMO was 99% honest. Any fault rests on my shoulders, a failure to ask ALL the questions.
I was lucky, the boat was in fantastic shape. Only one question should have been asked and answered. My fault. It has not affected the performance of the boat.
I have never heard of any broker or surveyor recommend not buying a boat because of known or hidden problems. Brokers will not volunteer information. As a buyer, you must investigate all aspect of the boat and then ask the questions. Finally, 'to purchase or not purchase' rests firmly upon the buyer's shoulders.
I am done.

I have had my cutless squeak when I transited from cold water to warm. Guess the rubber swelled a bit (it was new) and gripped the shaft. Could hear it squeal at dead idle and when prop shaft coasted down going into neutral. Did it for like a year, but guess it has worn itself in and no more noise.

When investigating it I found the shaft was binding a bit when rotating by hand. No longer have that binding (smooth as buttah) and no more noise.

Do check the alternator belts, that can do it too, depending on elec system loads and belt tension.

A hole in a turbo air hose can make a heck of a noise, but will only be there at higher power settings.

Thanks for all the responses. I am going to replace the cutless bearing. Does anyone have experience doing that?

Just because a cutlass makes a noise, that's not the reason to replace it. Wear is what should be considered.

I have had noisy cutlass bearings, not sure a loud screech is one description...that might be tough for the one that's underwater..... does a twin GB have drive trins with upper cutlass bearings like a single with long shaftvlog tube?

lanceolson said:

Thanks for all the responses. I am going to replace the cutless bearing. Does anyone have experience doing that?

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Lance, is Jefferson Beach Marina still in operation? Might be a good place to start. There is or was a working marina near the water works on Jefferson Ave.

They are a bitch to get out.

There are tools you can build to pull then out but you can also saw them lengthwise and pull out with pliers, as below:

Thanks again. I think The cutless bearing closest to the engine is bronze?? and is in housing that contains the shaft flax seal also. From a drawing I have it looks like the whole housing is bolted to the shaft tube??

We had a similar thing happen on our older Hatteras when departing from San Jose del Cabo just after pulling out of the slip. Fortunately there is a very good boat yard about a half a click from the marina. It sounded like a cutlass bearing. Got the boat hauled and it turned out that the set screws that hold the cutlass bearing on the intermediate strut had corroded away and the entire cutlass bearing was spinning in the strut. obviously brass spinning against bronze strut made a really high pitched sound. Decided to change all 4 cutlass bearings while out. Had to re align shafts and do a sea trial. The yard did a beautiful job. If that had happened a 100 miles up the line out in the middle of nowhere it could have gotten ugly. Good thing we heard it pulling out of the slip.

lanceolson said:

Thanks for all the responses. I am going to replace the cutless bearing. Does anyone have experience doing that?

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Yes, my right hand cramped from writing a check to the boat yard that replaced 6 bearings on my boat.

Greetings,
Mr. l. Have you definitely determined that the noise IS the cutlass bearing(s) and completely eliminated other possible sources? It could rapidly become quite expensive changing parts because "it might be".

RT Firefly said:

Greetings,
Mr. l. Have you definitely determined that the noise IS the cutlass bearing(s) and completely eliminated other possible sources? It could rapidly become quite expensive changing parts because "it might be".

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It might be worth a few bucks to take a 'knowledge' person or perhaps a surveyor out for a ride and ask their opinion?
Start with an open ended question. "What do you think the source of that noise is?" Dont plant the answer in his/her mind. If you say, "Do you think that is caused by......?" Their response more thank likely will be, "Could be" or "Maybe."

Thanks all.. I am going to have the boat pulled and all bearings checked and replaced if necessary. I want to be sure that everything below water is good. If they find nothing at least I know under water stuff is ok.

where do i find this carbon brush

jimdavi said:

Mine was the shaft carbon brush as well.

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Hello, i have also twin 3208ta engines but where is this carbon brush located ?
best regards,
Patrick